Combination of apparatus and buffer structure

ABSTRACT

In an apparatus having movable members and a buffer therebetween, improved buffer structure which comprises rectangular spring wire stock wound to cylindrical helix form so that the outer edges of the stock are stretched and thinned. The helix is axially compressed to interengage its inner edges leaving axial spaces between the outer edges. Upon axial impact the convolutions distort to close the spaces, thus providing the buffer effect.

United States Patent 1191 Krembel, Jr.

1111 3,855,922 14 1 Dec. 24, 1974 4] COMBINATION OF APPARATUS AND BUFFERSTRUCTURE [75] Inventor: Frank Krembel, Jr., St. Clair Shores, Mich.

[73] Assignee: Columbia Marking Tools, Inc.,

Detroit, Mich.

22 Filed: Jan. 29, 1973 21 Appl. No.: 327,446

Berger 29/173 2,844,378 7/1958 Whistler et a1. 37/142 X 2,883,927 4/1959Egbert 101/4 3,039,758 6/1962 Gratzmuller 267/168 X 3,160,090 12/1964Diegel 197/6.7 X 3,397,012 8/1968 Krekeler 37/142 R PrimaryExaminerEdgar S. Burr I Assistant Examiner-Pau1 J. Hirsch Attorney,Agent, or FirmBarnes, Kisselle, Raisch & Choate 57 ABSTRACT In anapparatus having movable members and a buffer therebetween, improvedbuffer structure which comprises rectangular spring wire stock wound tocylindrical helix form so that the outer edges of the stock arestretched and thinned. The helix is axially compressed to interengageits inner edges leaving axial spaces be- [56] References Cited tween theouter edges. Upon axial impact the convolu- UNITED' STATES PATENTS tionsdistort to close the spaces, thus providing the 1,214,120 1 1917 Bayne267/168 x b ff effect, 1,436,079 11/1922 Black 267/168 X 2,427,358 91947 Kovach 101 3 R 13 Claims, 6 Drawing Figures as 92 as PATENTED DEC 24 I974 SHEET 1 95 g COMBINATION OF APPARATUS AND BUFFER STRUCTURE Such amarking tool conventionally comprises a pneumatic or hydraulic cylinderwith a piston and piston rod therein, the piston rod projecting throughone end wall of the cylinder and carrying a marking die for markingworkpieces. Such tools are used extensively in thereof which relativelyquickly results in serious damage or destructionof the tool. Where thepiston is retracted by a spring, effectiveness of the return spring iseven more quickly destroyed.

Conventional efforts to meet this problem have involved such expedientsas venting the cylinder so as to trap a cushion of air between thepiston and the end wall of the cylinder, and the provision of a metalsleeve positioned axially between the end wall and piston for absorbingthe thrust of the piston. These efforts have been unsatisfactory sincethe aircushion provides inadequate buffering and the sleeve ultimatelybecomes distorted and interferes with functioning of the tool.

The object of the present invention is to provide, in an apparatushaving relativelymovable members, a relatively simple, inexpensivebuffer structure which is improved to provide adequate buffering betweenthe members and which nevertheless will have an effective life virtuallyas long as that of the apparatus as a whole.

Generally, the invention contemplates the use of a series of elementseach having an edge and ends adjoining the edge at junctures spacedapart in the direction of relative movement of the members of theapparatus. The ends extend transversely of said direction. Thejuxtaposed ends of successive elements in the series are contiguousproximal to their junctures with the edges and, distal of theirjunctures, are spaced apart in said direction. The elements areresiliently distortable so that the spacing between juxtaposed ends isdiminished responsive to engagement of the apparatus members against endones of the elements in the series.

One form of the invention is shown in the accompanying drawings.

FlG. l is a side elevational view of a marking tool which embodies thepresent invention. FIG. 2 is a left end elevational view of the tool.

FIG. 3 is an enlarged scale elevational view of the tool with partsbroken away and shown in section to illustrate structural details.

FIG. 4 is a side elevational view of the buffer structure per se. I

FIG. 5 is an enlarged scale, partly diagrammaticsectional view of thebuffer structure and its mounting in the tool.

FIG. 6 is a further enlarged, fragmentary, partly diagrammatic sectionalview of a portion of the buffer structure.

Shown in the drawings is a marking tool 10 according to the presentinvention having a mounting bracket 12 anchored to a base '14 by bolts16. A succession of workpieces W is presentedto the tool on a conveyoror fixture represented at 18. Marking tool 10 has a cylinder 20 with aside wall 22 and ends closed by a front cap 24 and a rear cap 26threaded onto the side wall as shown in FIG. 3. The interior of cap 24defines a front end wall 28 of the cylinder and the interior of cap 26defines a rear end wall 30 of the cylinder. Bracket 12 has an aperturedupright leg 32 through which side wall 22 extends and leg 32 is anchoredbetween axially disposed shoulders 34 and 36 on side wall 22 and'cap 24,respectively. Bracket 12 has a base leg 38 which is anchored to base 14by bolts 16.

Side wall 22 has a cylindrical inner surface 40 within which a piston 42is disposed. A piston rod 44 on the piston projects slidably through anaxial opening 46 in the portion of cap 24 defining end wall 28. The freeend 48 of the piston rod has a socket 50 which receives a marking die52. The die is removably retained within the socket by means of aresilient modified U-shaped clip 54 havingone leg 56 extending over thetop of the piston rod and another leg 58 which projects removablythrough aligned locking' notches 60, 62 in the rod moved to the left asthe drawings are viewed by fluid under pressure introduced into theinterior of cylinder.

20 from a suitable conduit through a port 72 in cap 26. The fluid couldbe hydraulic or pneumatic and for purposes of this'disclosure, it willbe assumedthat air under pressure is employed.

The piston carries a seal 74 which is in sliding, sealing engagementagainst cylinder interior 40. When the air pressure in the cylinder isrelieved, piston 42 is returned to the rightas the drawings are viewedby a coil spring 76 disposed around rod 44 and compressed between endwall 28 and an axial disposed face portion 78 of the piston. Returnmovement of the piston is buffered by a coil spring 80 disposed betweena shoulder 82 on the piston and end wall 30.

A buffer 84 according to the invention is contained between end wall 28and an axially disposed shoulder 86 within cylinder 20. In the structureillustrated, shoulder 86 comprises a. diametral enlargement of cylinderinterior 40.

In the form of the invention illustrated, buffer comprises a length'ofspring metalwire having rectangular sectional shape wound into the formof a cylindrical helix. In the course of the winding, the-outer edgeportions 88 of the wire are stretched to an extent greater than theinner edge portions 90 with the result that the outer edge portions areaxially thinner than the junctures 96. When the helix is axiallycompressed to solid condition, juxtaposed end portions 98 interengagewhile the portions of the ends extending toward outer edges 88 divergefrom each other.

When the buffer 84 is assembled within cylinder 20,

a it surrounds both piston .44 and return spring 76. As

shown in FIG. 5, shoulder 86 engages axially against a radially outerportion of one end element 92 of the helix and the other end element 92is engaged against end-wall 28. Radially inner portions of elements 92are disposed in the path of movement of piston 42 toward end'wall 28.Buffer 84 may be inits axially expanded or free condition as illustratedin FIG. 4 or may be axially compressed so that juxtaposed end wallportions 98 are contiguous, that is to say touching or nearly touchingas illustrated in FIGS. 5 and 6. In most structures, the contiguousrelation will probably be preferred since a certain amount of space issaved.

In use, it will be assumed that marking toolhas been mounted on base-l4for marking a series of workpieces W and that conduit 70 has beenconnected with a two-way pneumatic valve 100. When a workpiece onconveyor or fixture 18 is positioned in alignment with tool 10, valve100 is actuated to introduce air under pressure through conduit. 70 andport 72 into the right hand end of cylinder 20 as the drawings areviewed. Piston 42, piston rod 44 and marking die 52 are advancedleftward to the intermediate dotted line position of FIG. 1 where themarkingdie strikes the workpiece with sufficient force to impress theimage on the die into the workpiece. When valve 100 is actuated-toexhaust air under pressure from within the cylinder, piston 42 togetherwith rod 44 and die 52 are retracted to the right by return spring 76.The next time'a workpiece is aligned with tool 10, the cycle isrepeated.

Should the overall apparatus of FIG. 1 continue to cycle while empty ofworkpieces, valve 100 would be operated in each cycle of operation tocause piston 42 to advance and be retracted. However, upon eachadvancing stroke. piston rod 44 would be permitted to travel to theextreme leftward position illustrated in dotted lines in FIG. 1 and itis under these conditions that buffer 84 becomes effective. During thework or advancing stroke of the piston, its end face 78 strikes theright hand end of the buffer and if the buffer is not already axiallycompressed so that juxtaposed en'd portions 98 are interengaged, itbecomes so compressed in a further short increment of movement of thepiston. Thereafter, the buffering action of buffer 84 occurs.

As the force exerted by the piston on the buffer increases, elements 92distort resiliently in such a way i that the spaced apart portions ofjuxtaposed ends 94 move toward each other thereby closing or partiallyclosing the axial space therebetween as represented in dotted lines inFIG. 6. When pressure is relieved in the cylinder, spring 76 retractspiston 42 and elements 92 return resiliently from the dotted linecondition to the 10 is cycled without a workpiece W before it, thedescribed buffering action of buffer 84 takes place.

Description of a typical working tool follows. Piston 42 has a diameterof l 43 inch, a stroke of 2% inches and is actuated by air underpressure 60 P.S.I. Buffer 84 is made from spring steel wire A; inch by43 inch square and has a free length of about 1.72 inch. The buffer hasa solid length, that is a length wherein juxtaposed wall portions 98 aretouching, of about 1.585 inch. When the tool is cycled without aworkpiece in place, the piston delivers a blowagainst buffer 84 of about3 tons. The buffer compresses axially about 0.028 inch under this blow.A tool having these specifications has been cycled hundreds of thousandsof times in a test fixture with no workpieces and in each cycle allowingthe piston to deliver its full impact against buffer 84. This testresulted in no damage to the buffer or other components of the tool.

While end wall 28 is sloped with respect to the compression direction ofbuffer 84,,it is believed that this slope does not significantlycontribute to the relative closing movement of juxtaposed ends 94 sincethe same phenomenon has been observed where the buffer has beencompressed between members extending perpendicular to the axis'of thebuffer. However, it is believed that the angle of elements 92 relativeto a plane perpendicular to the axis of buffer 84 may contribute to thephenomenon. In the typical tool described above, this angle is about 6degrees when the buffer is compressed so that end portions 98 aretouching.

While buffer 84is illustrated as being in the form of a single wirewound to a cylindrical helix, it will be appreciated that elements 92could comprise individual rings having the'sectional shape illustratedin FIGS. 5

and 6 andmounted with juxtaposed ends in contiguous relation as at 98.Moreover, in some apparatus, elements 92 could advantageously be madeasa series of bars having the sectional shape of FIGS. 5 and 6 with endportions 98 thereof contiguous.

I claim:

1. Apparatus which comprises,

two members assembled for relative movement wherein respective portionsthereof approach each other,

a buffer comprising means defining a series ofelements disposed betweensaid portions,

each of said elements having an edge and ends adjoining said edge andforming junctures therewith,

solid line condition illustrated in'FIG. 6. Each time tool said. endsextending transversely of the direction of said movement and thejunctures between said ends and edgebeing spaced apart in saiddirection,

said members, responsive to said relative movement thereof, beingeffective to exert force on the end ones of said elements in saidseries,

said pairs of aligned proximal portions being interengaged when saidforce is so exerted,

said continuously extending portions cooperating to form a solid columnin said direction when .said proximal portions are so interengaged,

said elements being resiliently distortable so that, re-

sponsive to an increase of said force upon further said relativemovement of said members, the spacing between said distal portions ofsaid juxtaposed pairs of ends is diminished.

2. The apparatus defined in claim 1 wherein said elements extendarcuately about a common axis generally parallel to said direction.

3. The apparatus defined in claim 2 wherein said means comprises ahelical wound length of resiliently said ends extending transversely ofthe direction of said movement and the junctures between said ends andedge being spaced apart in said direction,

said ends of successive elements in said series being arranged injuxtaposed pairs, said ends of each juxtaposed pair having portionsproximal to said junctures which are relatively close together, saidends of each juxtaposed pair having portions distal of said junctureswhich are spaced relatively further apart in said direction than aresaid proximal portions, said proximal portions of said ends beinggenerally aligned in said direction, said members, responsive to saidrelative movement thereof. being effective to exert force on the endones of said elements in said series, said pairs of aligned proximalportions being interengaged when said force is so exerted, said elementsbeing resiliently distortable so that, re-

sponsive to an increase of said force upon further said relativemovement of said members, the spacing between said distal portions ofsaid juxtaposed pairs of endsis diminished. each of said elementshavinganother edge shorter than the first mentioned edge, said end adjoiningsaid other edge, each of said elements having a sectional shape in whicheach of said edges and ends extends along a generally straight line,said means comprising a helical wound length of resiliently distortablematerial, the helix having an axis generally parallel to said direction,said elements comprisingsuccessive turns of the helix. 5. The structuredefined in claim 4 wherein said means comprises a length of spring metalstock initially having rectangular sectional shape and being wound tocylindrical helical form, said elements comprising successive turns ofthe helix,

the first-mentioned edge and said other edge of each element beingdisposed respectively inwardly and outwardly of said helix.

6. The apparatus defined in claim 5 wherein said members comprise acylinder and a piston movable therein by fluid under pressure, saidportions comprising an end wall of said cylinder and a radiallyextending face of said piston.

7. The apparatus defined in claim 6 and including means defining aradially extending shoulder in said cylinder, said buffer beingcontained between said end wall and shoulder, a portion of said bufferprojecting radially inwardly of said shoulder into the path of movementof said piston face.

8. The apparatus defined in claim 7 wherein said shoulder comprises adiametral enlargement of the cylinder interior.

9. The apparatus defined in claim 6 wherein a piston rod on said pistonextends through said buffer and to the exterior of said cylinder.

10. The apparatus defined in claim 9 wherein a helical return springcompressed between said end wall and said piston face is disposed aroundsaid piston rod and within said buffer.

11. The apparatus defined in claim 9 wherein said piston rod has anouter end provided with a tool for performing work on a workpiece.

12'. The apparatus defined in claim 11 wherein said tool comprises amarking die.

13. A marking tool which comprises,

a cylinder and a piston movable therein by fluidpressure, a rod on thepiston extending through an end wall of the cylinder, and a marking diecarried by the rod,

a buffer comprising a length of spring metal stock initially havingrectangular shape and beingwound to cylindrical helical form so that theouter edges of.

the stock are stretched and have shorter axial,

length than the inner edges of the stock,

successive turns of the helical form having ends which extend generallyradially, face generally axially and adjoin said inner edges atjunctures,

said ends of said successive turns being arranged in juxtaposed pairs,said ends of each pair having portions proximal to said junctures whichare relatively close together,

said ends of each pair having portions distal of said junctures whichare spaced relatively further apart in an axial direction than are saidproximal portions, 1

means containing said form axially between said end wall of saidcylinder and said piston so that portions of said form defining saidjunctures and portions of said form radially outwardly thereof aredisposed in the path of relative advancement of said piston and end walltoward each other,

said piston and end wall being effective to exert force on the end onesof said turns of said helical form upon said relative advancement,

said pairs of aligned proximal portions being interengaged when saidforce is so exerted,

said turns being resiliently distortable so that, responsive to anincrease of said force upon further said relative advancement, saidspacing between said distal portions of said juxtaposed pairs of ends isdiminished.

1. Apparatus which comprises, two members assembled for relativemovement wherein respective portions thereof approach each other, abuffer comprising means defining a series of elements disposed betweensaid portions, each of said elements having an edge and ends adjoiningsaid edge and forming junctures therewith, said ends extendingtransversely of the direction of said movement and the junctures betweensaid ends and edge being spaced apart in said direction, said ends ofsuccessive elements in said series being arranged in juxtaposed pairs,said ends of each juxtaposed pair having portions proximal to saidjunctures which are relatively close together, said ends of eachjuxtaposed pair having portions distal of said junctures which arespaced relatively further apart in said direction than are said proximalportions, said proximal portions of said ends being generally aligned insaid direction, each of said elements having portions which extendcontinuously in said direction between said proximal portions thereof,said members, responsive to said relative movement thereof, beingeffective to exert force on the end ones of said elements in saidseries, said pairs of aligned proximal portions being interengaged whensaid force is so exerted, said continuously extending portionscooperating to form a solid column in said direction when said proximalportions are so interengaged, said elements being resilientlydistortable so that, responsive to an increase of said force uponfurther said relative movement of said members, the spacing between saiddistal portions of said juxtaposed pairs of ends is diminished.
 2. Theapparatus defined in claim 1 wherein said elements extend arcuatelyabout a common axis generally parallel to said direction.
 3. Theapparatus defined in claim 2 wherein said means comprises a helicalwound length of resiliently distortabel material, said elementscomprising successive turns of the helix.
 4. Apparatus which comprises,two members assembled for relative movement wherein respective portionsthereof approach each other, a buffer comprising means defining a seriesof elements disposed between said portions, each of said elements havingan edge and ends adjoining said edge and forming junctures therewith,said ends extending transversely of the direction of said movement andthe junctures between said ends And edge being spaced apart in saiddirection, said ends of successive elements in said series beingarranged in juxtaposed pairs, said ends of each juxtaposed pair havingportions proximal to said junctures which are relatively close together,said ends of each juxtaposed pair having portions distal of saidjunctures which are spaced relatively further apart in said directionthan are said proximal portions, said proximal portions of said endsbeing generally aligned in said direction, said members, responsive tosaid relative movement thereof, being effective to exert force on theend ones of said elements in said series, said pairs of aligned proximalportions being interengaged when said force is so exerted, said elementsbeing resiliently distortable so that, responsive to an increase of saidforce upon further said relative movement of said members, the spacingbetween said distal portions of said juxtaposed pairs of ends isdiminished. each of said elements having another edge shorter than thefirst mentioned edge, said end adjoining said other edge, each of saidelements having a sectional shape in which each of said edges and endsextends along a generally straight line, said means comprising a helicalwound length of resiliently distortable material, the helix having anaxis generally parallel to said direction, said elements comprisingsuccessive turns of the helix.
 5. The structure defined in claim 4wherein said means comprises a length of spring metal stock initiallyhaving rectangular sectional shape and being wound to cylindricalhelical form, said elements comprising successive turns of the helix,the first-mentioned edge and said other edge of each element beingdisposed respectively inwardly and outwardly of said helix.
 6. Theapparatus defined in claim 5 wherein said members comprise a cylinderand a piston movable therein by fluid under pressure, said portionscomprising an end wall of said cylinder and a radially extending face ofsaid piston.
 7. The apparatus defined in claim 6 and including meansdefining a radially extending shoulder in said cylinder, said bufferbeing contained between said end wall and shoulder, a portion of saidbuffer projecting radially inwardly of said shoulder into the path ofmovement of said piston face.
 8. The apparatus defined in claim 7wherein said shoulder comprises a diametral enlargement of the cylinderinterior.
 9. The apparatus defined in claim 6 wherein a piston rod onsaid piston extends through said buffer and to the exterior of saidcylinder.
 10. The apparatus defined in claim 9 wherein a helical returnspring compressed between said end wall and said piston face is disposedaround said piston rod and within said buffer.
 11. The apparatus definedin claim 9 wherein said piston rod has an outer end provided with a toolfor performing work on a workpiece.
 12. The apparatus defined in claim11 wherein said tool comprises a marking die.
 13. A marking tool whichcomprises, a cylinder and a piston movable therein by fluid pressure, arod on the piston extending through an end wall of the cylinder, and amarking die carried by the rod, a buffer comprising a length of springmetal stock initially having rectangular shape and being wound tocylindrical helical form so that the outer edges of the stock arestretched and have shorter axial length than the inner edges of thestock, successive turns of the helical form having ends which extendgenerally radially, face generally axially and adjoin said inner edgesat junctures, said ends of said successive turns being arranged injuxtaposed pairs, said ends of each pair having portions proximal tosaid junctures which are relatively close together, said ends of eachpair having portions distal of said junctures which are spacedrelatively further apart in an axial direction than are said proximalportions, means containing said form axially between said end wall ofsaid cylindeR and said piston so that portions of said form definingsaid junctures and portions of said form radially outwardly thereof aredisposed in the path of relative advancement of said piston and end walltoward each other, said piston and end wall being effective to exertforce on the end ones of said turns of said helical form upon saidrelative advancement, said pairs of aligned proximal portions beinginterengaged when said force is so exerted, said turns being resilientlydistortable so that, responsive to an increase of said force uponfurther said relative advancement, said spacing between said distalportions of said juxtaposed pairs of ends is diminished.